#include <iostream>
int main(int argc, char const *argv[])
{
    using namespace std;
    int dec = 42;
    //16进制，以0x或0X
    int dex = 0x42;
    int oct = 042;
    cout << "42 is : " << dec << endl;
    cout << "0x42 is : " << dex << endl;
    cout << "042 is : " << oct << endl;
    return 0;
}
